The present invention relates to a liquid crystal display device, and particularly to a technology which is effective by being applied to a liquid crystal display device used in a portable electronic instrument.
To date, a liquid crystal display device (which may also be called a liquid crystal display module) is used in a display of a portable electronic instrument, such as a portable telephone terminal or a PDA.
The liquid crystal display device has a liquid crystal display panel having a liquid crystal material enclosed between a pair of substrates. The display area of the liquid crystal display panel is configured of a collection of pixels, each of which has a TFT element, a pixel electrode, a common electrode, and a liquid crystal material. At this time, the luminance (gradation) of each pixel is controlled by changing the orientation of liquid crystal molecules in the liquid crystal material by means of an electric field whose intensity varies depending on a potential difference between the pixel electrode and common electrode.
Also, when displaying a video or image on the liquid crystal display device, a deterioration in image quality is prevented by, for example, reversing a relationship in each pixel between the potential of the pixel electrode and the potential of the common electrode for each frame period.
Furthermore, when displaying a video or image on the liquid crystal display device, a deterioration in image quality is prevented by, for example, mixing a pixel in which the potential of the pixel electrode is made higher than the potential of the common electrode, and a pixel in which the potential of the pixel electrode is made lower than the potential of the common electrode, for one frame period.
As a method of providing the pixel in which the potential of the pixel electrode is made higher than the potential of the common electrode, and the pixel in which the potential of the pixel electrode is made lower than the potential of the common electrode, there are, for example, a drive method called a line inversion drive, and a drive method called a dot inversion drive. The line inversion drive is a drive method such that, for one frame period, in pixels aligned in a direction of extension of video signal lines, the relationship between the pixel electrode potential and common electrode potential is the same, and in two pixels adjacent to each other across a video signal line, the relationships between the pixel electrode potential and common electrode potential are opposite ones. Also, the dot inversion drive is a drive method such that, for one frame period, in two pixels adjacent to each other in the direction of extension of the video signal lines, as well as in two pixels adjacent to each other across a video signal line, the relationships between the pixel electrode potential and common electrode potential are opposite ones.
Meanwhile, with a heretofore known liquid crystal display device, in general, the number of terminals of a driver IC which applies video signals to video signal lines is equal to the number of video signal lines. However, as a recent liquid crystal display device, for example, one has been proposed in which the number of video signal input terminals on a liquid crystal display panel is made less than the number of video signal lines disposed in a display area, and a switch circuit is interposed between the video signal input terminals and video signal lines (refer to, for example, JP-A-2002-372955).
With this kind of liquid crystal display device, one video signal input terminal being connected to, for example, each of three adjacent video signal lines via switch elements, signals applied to each of the three video signal lines are applied to the one video signal input terminal for a period for which one scan signal line is being selected. Then, by activating and deactivating the switch elements for the period for which one scan signal line is being selected, video signals applied to the one video signal input terminal are applied, distributed, to the three video signal lines. With this kind of liquid crystal display device, it is possible to reduce the number of output terminals of the driver IC to one third, even with the same resolution as that of the heretofore known one. For this reason, it is possible to hope for an enhancement in resolution (an enhancement in definition) of a compact liquid crystal display device used in the display of the portable electronic instrument.